Is your value list a custom value list or did you set it up with "use values from a field"? There are a couple of ways that you can introduce what I refer to as "control" values into the value list--even if it is based on values from a table. A script trigger can then perform a script when you select from the value list and this script can do different things if the value selected was "-All-" than when it selected value to use for performing a find.
For table based value lists, here are two ways to add a control value to the list:
- Add a record with the control value in the field where you'd otherwise have the name. That can work fine for tables dedicated for use in a value list, but if the table is also used for other purposes, you may need to exclude those added records and that can be a problem.
- Define a calculation field in the value table defined as: List ( "-All-" ; ValueField ) and update your value list to list values from this calculation field instead of ValueField.
It's a bit ironic. I've been doing this exact thing for an iPhone DB just an hour ago and posting this message is pointing out to me that I've been focused on the first option when the second might be a better choice for my particular design.